In one new psychobiologic study, cerebrospinal fluid (CSF) concentrations of the neuropeptides vasopressin, corticotropin-releasing hormone, and somatostatin, which in our previous studies were elevated in obsessive- compulsive disorder (OCD) patients, were found to be reduced during treatment with the serotonin reuptake inhibitor clomipramine. In another study, individuals with subclinical checking behavior had impaired memory of prior actions, providing a new indication of cognitive contributions to compulsive behaviors. In preclinical animal model studies, development of food restriction- induced compulsive running in rats was prevented by chronic treatment with serotonin reuptake blockers but not antidepressants which are in effective for OCD treatment. In continuing studies of OCD comorbidity, patients with bulimia nervosa assessed by structured diagnostic interviews were found to have an increased incidence of lifetime diagnoses of OCD. In a separate larger study, severity of eating disorder symptoms in bulimic patients correlated with measures of OCD symptom severity, and OCD symptoms abated during behavioral treatment for bulimia.